AW: assert in phylink.c with lan7801 and dp83tc811 since kernel 6.18

[Sven Schuchmann <schuchmann@schleissheimer.de>]

Hi Andrew,

I came up with this:

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 261af300ab00..734cb62a1043 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2862,7 +2862,9 @@ static int lan78xx_phylink_setup(struct lan78xx_net *dev)
 static void lan78xx_phy_uninit(struct lan78xx_net *dev)
 {
        if (dev->phylink) {
+               rtnl_lock();
                phylink_disconnect_phy(dev->phylink);
+               rtnl_unlock();
                phylink_destroy(dev->phylink);
                dev->phylink = NULL;
        }

and it seems to prevent the cash. What do you think?


Reards,

   Sven

Von: Andrew Lunn <andrew@lunn.ch>
Gesendet: Dienstag, 05. Mai 2026 15:13
An: Sven Schuchmann <schuchmann@schleissheimer.de>
Cc: netdev@vger.kernel.org <netdev@vger.kernel.org>
Betreff: Re: assert in phylink.c with lan7801 and dp83tc811 since kernel 6.18


On Tue, May 05, 2026 at 09:53:06AM +0000, Sven Schuchmann wrote:

> Hello,
> I have a raspberrypi and switched from kernel 6.12 to 6.18 and now I have a crash in phylink.c.

Please could you try 7.0.3, or better still, 7.1-rcX. We need to
determine if the problem has already been fixed and just needs
backporting, or is it a new problem.

> I am using a MAC:lan7801 and PHY:dp83tc811 and now it crashes like this:
>
> [    3.019174] usb 1-1.3: New USB device found, idVendor=0424, idProduct=7801, bcdDevice= 3.00
> [    3.021152] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> [    3.023192] usb 1-1.3: Product: LAN7801
> [    3.025019] usb 1-1.3: Manufacturer: Microchip
> [    3.026772] usb 1-1.3: SerialNumber: 00800F780100
> [    3.078542] lan78xx 1-1.3:1.0 (unnamed net_device) (uninitialized): int urb period 64
> [    3.091434] lan78xx 1-1.3:1.0 (unnamed net_device) (uninitialized): validation of rgmii-id with support 0000000,00000000,00000000,00006280 and advertis                                      ement 0000000,00000000,00000000,00006280 failed: -EINVAL

This appears to be the real problem.

> [    3.098928] lan78xx 1-1.3:1.0 (unnamed net_device) (uninitialized): can't attach PHY to usb-001:004, error -EINVAL
> [    3.101094] ------------[ cut here ]------------
> [    3.103163] RTNL: assertion failed at drivers/net/phy/phylink.c (2337)

and this is a knock on problem, which normally you don't see.
Please could you make line 1 of drivers/net/phy/phylink.c.

#define DEBUG 1

That will give us additional debug info.

     Andrew